Wireless communication systems are widely deployed to provide various types of communication such as voice and data. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other multiple access techniques. A CDMA system provides certain advantages over other types of systems, including increased system capacity.
A CDMA system may be designed to support one or more CDMA standards such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the Wide-band Code Division Multiple Access (W-CDMA standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems” (the IS-2000 standard), and (4) some other standards. An example non-CDMA system is the Global System for Mobile communication (GSM) system.
Neighboring systems may employ one or more radio access technologies on one or more frequencies. Furthermore, a system may have one radio access technology overlaying another. For example, portions of a GSM system may be overlapped with W-CDMA base stations. It may be desirable for a mobile station communicating on the GSM system to handoff to the W-CDMA system without dropping an active call.
To facilitate such handoff, a mobile station must periodically search for base stations on alternate frequencies and/or alternate radio access technologies. In some communication systems, a list of potential neighboring base stations is transmitted from a base station to a mobile station. This list is commonly referred to as a neighbor list. By limiting searches to those base stations on the neighbor list, a mobile station can reduce the amount of time required for such searching. However, when searching is required on an alternate frequency, the time available for such searching may be limited while an active call is in session. There is therefore a need in the art for inter-frequency neighbor list searching.